International mailings required denominations at one time, but the rules have changed and the post office issues "forever" stamps for international purposes. In the postal store, these are called "global forever" stamps. Example: https://store.usps.com/store/browse/uspsProductDetailMultiSkuDropDown.jsp?categoryNav=false&navAction=push&navCount=0&atg.multisite.remap=false&categoryId=buy-stamps&productId=S_564504

An international forever stamp has a value of $1.15. Postcards and one-ounce letters to any international destination currently cost $1.15, so that international forever stamp is good for a postcard or a one-ounce letter (usually about 4 pages of paper). See page 47 of the post office's Notice 123 (the regular price list): https://pe.usps.com/cpim/ftp/manuals/dmm300/Notice123.pdf