They may not be on there. Several years ago there used to be a specific box for them, but not on the newer 1098 forms. You may find property taxes in box 10, which is "other." If not, and you don't have your own records, then you'll have to locate the amount in another way.
A phone call to your lender might be the easiest way to get the figure. Also, many counties/municipalities have a property tax database on their web sites, where you can enter some identifying information and then see your annual property taxes going back a number of years.