Upsizing pants?

I have a few like-new pairs of cargo pants that have been sitting around for several years. Pulling them out yesterday, I realize they’re a size (or two?) too small for me. Particularly around the waist and butt, not so much around the legs and not too short.

Being newish to sewing, wearables, and alterations, should I aim for panels on the outseams? (there are pockets there) Or inseams? Or is there another trick?

Or am I being ambitious and should just donate or repurpose them for something else? I love the pants and material, but they don’t fit anymore! (Laughing because losing weight is an option, but not happening in the near future) My real ambition is to make my own fitted pair of cargo pants someday.