Flash player

Easy. Go here and download "Flash Player Projector" https://www.adobe.com/support/flashplayer/debug_downloads.html

That should allow you to play any properly functioning .swf files you have saved offline provided they dont need internet to work. Just install it and open your swf files with it.

If you want to view flash online perhaps try SuperNova SWF Enabler.

Many sites are also working on alternatives to Adobe Flash to allow flash playback. Some of them you can tell others about are. Shumway, Ruffle.rs, Waflash, Apache Royale, and CheerpX.

Some sites like Newground or kongregate are trying site specific methods that may require an extra step on your part. Keep in mind that among the sites with working flash you will likely need to click the spot where the flash file should have loaded and then tell your device to allow flash to play.

Im noticing a common error in trying to run flash with ruffler.rs is things will freeze and not load the file. Please keep in mind that solutions are being worked on by many.

Some Flash archives to test if things are working well.

https://bluemaxima.org/flashpoint/
https://archive.org/details/softwarelibrary_flash

Can really be called a flash archive but you can test things here. www.albinoblacksheep.com or https://dagobah.net

Flash Player has always been a free download.

Flash Player has reached end-of-life and all supported browsers will soon be removing Flash support.  The schedule depends on the browser vendor.

You can't always get what you want.