See the Help Center article
Retention of Records. It echos and adds to the instructions in
General Handbook, 33.9.2. The principal is "Records should be kept only as long as they are needed for administrative, legal, and historical purposes." Membership record retention information for ordinances is normally 1 year. But the forms used to create records not pertaining to ordinances, such as a child record form (not to be confused with a baptism form), can be destroyed once they have been uploaded since the image is now saved on Church data servers. You can take a precautionary approach and retain those forms for 1 year.