I want to hook up a laundry sink to existing pipes which requires pexs tubing. There are no turn off valves only pipes coming out.

We will try to move this to plumbing where you will get better answers. In the meantime maybe you can give more details. Your 2 PEX pipes must have a shut off somewhere otherwise water would be running out of them right now. Try to find where they are valved. Is there a drain, if so how large?