Q: remove my old iphone from my find my phone

https://www.icloud.com/#find

If it is not listed on iCloud.com in the find my iPhone section, then the iPhone 5 most likely no longer has find my iPhone active.

If you can access your iCloud account on a browser on your PC and your old iPhone is not listed (assuming it used the same Apple ID) then it is not there. Maybe you used a different ID. I don't know what you are trying to accomplish but you could always contact Apple ID Support, they would help.

Apple ID - Official Apple Support