Help converting to a single chainring

I have a Scott Aspect 740 that I want to convert over to a single chainring in the front. I currently have a Shimano FC-M3000 on it. I want to change it to a single 30t ring but can't figure out what bolt circle size ring I need to order. Also, other then different bolts, what else do I have to do to make it 1 speed in the front?

I appreciate all the help!