Website started in 1998, need to do a massive update

There are many themes available in ThemeForest and other marketplaces. You can check out there hope you find out there

Have a look at this playlist

https://www.youtube.com/playlist?list=PLUjqTJN3byC9fUoXFnoNGlYBCBZOJUPca

JenL5, thanks so much. I will give this a shot and see if I can dig myself out my obsolescence.

Don't be intimidated by the curreny iteration of Dreamweaver. It's not just for exclusive minded coders--designers and artists can certainly use it too--you don't mind learning something new. You can update or to scrap the whole site and start over. Dreamweaver IS a different application than it (or GL) used to be, perhaps not for the best, but workable.

Start here and view the tutorials on setting up a responsive site: https://helpx.adobe.com/dreamweaver/tutorials.html

I am working on a similar type project myself. First designed the site in about '99 with DW (I think) and changed to Go Live at some point. Continually updated the site through 2020, until my workhorse MacPro with legacy SW started having issues. So I taught my self DW using the tutorials. If you have the time, it's possible. I personally ruled out other web development SW because of lack of portability, or inability to to make highly customized elements, or cost (over years). Good luck!

@osgood_and  @Nancy OShea have already said what have to be said...

In one side, run using Bootstrap and develop your website as you would like, a bit like building a kitchen by buying prefabricated cupboards that you assemble... (I don't know if I can name brands, but I guess you know what I mean),

Or in an other side, use a CMS like Wordpress that will take care of most of your interaction and data management needs

In both cases you can start from an external template acquired from various specialized platforms https://themeforest.net/ , but not only https://webmetools.com/themeforest/alternatives

I would like to open a third door, so my question, would concern your current content, would you like to start from scratch, or would you like to start from the existing one by adapting the technologies and structure constructions in a more contemporary way.

I remember that when your site was developed, in the late 90's, the debate between using or not using CSS was topical. and at that time, Christopher Schmitt, in parallel with his books on CSS, had set up a series of tools that allowed for these switches between table and CSS sites. There were many articles on the Macromedia devnet.

Anyway, what ever your choice, will be , it is important before starting such an enterprise to study a benefits / risks balance.

Java is not the same as JavaScript. Two different things.  JavaScript is required learning if you intend to build modern websites. 

Unfortunately, print design has about as much in common with the web as elephants and tea leaves.  The web is not a one-size-fits-all universe the way print is.  Site visitors must be able to access your site from ALL sized devices, not just desktops.  Also the web is a lot more complicated now than it was 5-10 years ago.  Dreamweaver is just a glorified coding tool.  Tools don't build websites, people do.  

If your site is important, spend the money to hire an experienced developer to rebuild your site.  Or else, rebuild it with an online web service or CMS platform like WordPress so you don't have to look at code.   

There isn't any tools in Dreamweaver that l would recomend because its mainly a coding based application these days.

Your background, which seems to lack in code knowledge, sounds as though you might benefit from using a framework like Bootstrap, which might be suitable for someone who is happy to play 'coloring by numbers' and doesn't want to learn much about the fundamentals of web development.

However Dreamweaver currently only has Bootstrap 4 as its main tool, which is an out dated version. It will get the job done but you'll be starting out already behind the curve. It would be more sensible to use Bootstrap 5 but you will have to copy and paste components from the official Bootstrap 5 website and use Dreamweaver as an editor.

Personally l don't recomend Bootstrap at all but it may serve a purpose in some cases. I would always recomend  building a website yourself but you need the skills and knowledge to do so and using a workflow like flexbox or css grid.

Maybe you should investigate WordPress, Webflow or some other low code tooling which negates some of the coding skills which are required to  build websites