Yes, of course, (1) as long as the studies there satisfy your pre-planned eligibility criteria and (2) especially when the studies you find in The Cochrane Library have no record in other databases. The Cochrane Library is a well-recognized database for scouring publications for systematic reviews, since it is maintained by the Cochrane Collaboration which is a leading organized network of professional systematic reviewers. Besides, the goal of a systematic review is to analyze and derive evidence from all available published and unpublished studies that attempt to answer your specific review question - and one way of ensuring good coverage is to do searching on as many databases as efficiently possible.

so i can simply use that to make a dataframe to analyse in library like metafor?

Yes, you can. As Cochrane Library is a central database, you should search it. If you don't get any relevant studies using your search strategy, you can ignore the database.

Thank you.