how to upgrade iPhoto to photo

My MacBook Pro is over 10yrs old and while I had my old battery swapped out for a new one in '18, nothing else was updated. It's over capacity, I use multiple portable hard drives, and would appreciate help with how to open the photos I used to be able to access via iPhoto.

I keep getting an error message asking me to upgrade to Photo. Apologies if I am asking a probably dumb question.