when i downloaded the linux version, i couldnt find the .exe file i needed and i looked every where
There is no .exe. To run the Linux version you run the file named "V1.04_Raft_LinuxUniversal.x86" or ".x86_64".
Linux doesn't use .exe to know that it's a program. It uses a permission setting on the file.
But I'd be surprised if you could run any game like this on a Chromebook unless you've rooted it.