I can’t find any codes to have nonstop on project 64 and I want to try the speed run. All codes so far don’t work

In PJ64 v1.6.x, you can add codes by right-clicking the SM64 ROM you want to play > Edit Cheats > right-click > Add New Cheat...
Nonstop can also be played on the Usamune practice ROM, but you must turn off all other options/codes besides the required ones for nonstop (if you plan to submit to the leaderboard).

The correct nonstop codes can be found on the rules tab of the Nonstop leaderboards: https://www.speedrun.com/sm64ce#Nonstop

I'll also post them here for convenience. Note that the codes are different depending on the region of the ROM.

Nonstop:
US:
8124DDBC 2400
8124DE1C 2400

JP:
8124DC1C 2400
8124DC74 2400

Skip Intro:
US: 8124BBD4 2400
JP: 8124BA34 2400

Soft Reset (A+B+Z+Start):
US:
D133AFA0 F000
8033B239 0004
D033B26B 0000
8033B239 0001

JP:
D1339C30 F000
80339EC9 0004
D0339EFB 0000
80339EC9 0001

Ok, I have usamune and I have pj64 v3.something, I haven’t gotten 1.6 because I didn’t know I had to use it until a little bit ago but I didn’t know that usamune was allowed on the leaderboard. Or is it not?

If you ever plan to submit runs to the leaderboards, I highly recommend just downloading and setting up PJ64 v1.6.x. Here is where to find it, with instructions on how to set it up properly: https://wermi.neocities.org/emuguide/getting_emu/#download

Usamune is not allowed for most categories, but there are a few exceptions such as Nonstop. But again, you would have to disable all options except for intro skip and the nonstop option (which sounds like a hassle to me if you have most options turned on in the first place).