The number of pre-approvals you should get depends on a few factors, including how long you plan to stay in your home and how many lenders you want to compare. If you're planning on staying in your home for a long time, it may be worth getting multiple pre-approvals to compare rates and terms from different lenders.
However, if you're not sure how long you'll stay in your home or if you only want to compare a few lenders, one or two pre-approvals should be sufficient. Ultimately, the decision of how many pre-approvals to get is up to you and will depend on your unique circumstances.