need to autorun a program at startup on ubuntu server 21.04

I need to autorun a program at startup on ubuntu server 21.04 . I have worked on this for days with no result. I tried @reboot but it does not work. I tried to look at the logs but did not find anything or error messages. I want to run a bash script (.sh) that cd to a folder and then runs a c program. The machine I am running on is a raspberry pi 3B. it is holding up my project that I need to install. Thank you for your help.