Opened mac to download some photos only to realize thousands of my photos are gone becasue they were stored in the "iphoto" app that is no longer supported. Anyway I can regain access to my lost photos? Photos are not found within the "photos app".

You were warned. iPhoto ceased development and was removed from sale almost 5 years ago. Apple have been saying that they would drop 32 bit support for the past two years. There were specific announcements for iPhoto and Aperture in the spring of this year. iPhoto was replaced by the more powerful (and free) Photos, again, almost 5 years ago. You can migrate from iPhoto to that app very simply:

Hold down the option (or alt) key and launch Photos. From the resulting menu select 'Choose Library' and point at your iPhoto Library. It will do the rest.

If you prefer not to use Photos there are several 3rd party apps that you can use. Which to choose depends on the kind of photographer you are and your budget.

HollyBH4321 wrote:

Opened mac to download some photos only to realize thousands of my photos are gone becasue they were stored in the "iphoto" app that is no longer supported.

Your photos have not been stored in the iPhoto.app but in an iPhoto Library. Is your iPhoto Library still there? By default it will be in the Pictures folder. Where did you you keep your iPhoto Library?

Photos are not found within the "photos app" or within finder.

If you already launched Photos and it does not show your iPhoto Photos you have to point Photos to the library location, as described by TD in the post above.