Filemaker's layout wizard supports a selected number of avery label layouts. If your labels aren't in the list, you can check to see if one of the listed formats is the same (avery numbers also identify the material the label is made from, check the packaging for any info that lists avery format numbers that have the same label dimensions).
If all else fails, you may have to create your own labels layout. This can be done as long as you pay careful attention to the dimensions of each part of your label page, including margins and any "gutter" that creates spacing between the labels. The inspector can help you specify an exact height for the header, body and footer and you can specify margins in layout setup... on the Printing tab.