Export > Filename > Sequence: Start file names with sequence number, and zeros, ex: 001_filename.jpg

As you have discovered you can build your own filenaming pattern from ‘tokens’ as well as including fixed text or separating characters.

Just for completeness, for any others reading along: if you choose “01” this limits you to a 00-99 range - so there are also “001” or “0001” options. 

Furthermore, there are two numbering alternatives - one way LrC starts afresh for each exported batch, so that numbering is not unique: each new export batch includes its own image number 1, 2 etc. The other way LrC carries on incrementing from whatever highest number was used in a previous export. That may need more digits but keeps each successive number unique.

Either way, a later repeated export of a given image is either certain not to - or very unlikely to - be assigned the same numbering that it got the first time. Depending on chosen scheme you may get no prompt for overwriting (replacing) anything: the earlier and later exports will both remain. Or if you do, and you opt to overwrite an existing file, that could accidentally be the prior export for some other photo! So this numbering idea only makes sense when exporting entire batches entirely “fresh”.

I actually figured out how to do exactly what I wanted.

Export settings > File Name Rename To dropdown > Edit 

Mac and Windows put files in any sequence you want.  If you choose “file name” the it sorts them by the File name in either direction.   

The export dialog has a panel where you can select a file renaming template of your choosing.  this can be one that Adobe created and came with LrC or one you create yourself.  These are quite flexible.  When you create such a template you pick tokens that represent various things like a numberic sequence and you can select how many digits are used for those numbers.  

If give us an example of a short set of current file names for a series of images you want to export and what you want it to become for the exported file we can show you how to contruct the template.