Deleting existing old builds/Pull Requests

Hello. New here and new to Jenkins. Taking the course on Coursera. But at the moment, and after searching. I cannot find the answer to a question, or i am not asking it correctly.

I need to clean up space on a Jenkins installation and for the life of me i cant find information on how to do this. Just on how to set future jobs to self destruct after a certain number of days or a limited number of builds.

How do i delete old builds (some 2 years old)? There is no delete button that i can see when i click on a job.

Any guidance here would be great. I dont think i am near this topic yet in the coursera platform.

Thank You