Welcome to the forum.
Insofar as value, much depends on condition. These are common stamps.
Yours look as though they are clean and in good condition, although the individual stamps are not well centered. If the gum on the backs is in original unblemished condition you might sell them for a few dollars on eBay
. But collectors will prefer to see a scan of the back, too, so they know.
see ebay past sales of 689 blocks
Disregard the sales of plate number blocks, and look for sales of blocks without numbers, like the block of 8 back on Dec. 14
Hope this helps, though it is probably an eye-opener as to the state of the market for these.