Once you have these on hand, it’s easy to use MS Word to print on them by pages. Simply select: “Tools” > “Letters And Mailings” > “Envelopes and labels”
Once you are in there, you can find your paper size simply by selecting one of the 2 tabs and scrolling to find your paper size.
Once you find the size click:
“Add to Document” or “New Document” (new document if you are working with labels).