I don't think I can direct link this due to ROMS on the site and the guide itself being a very copyrighted PDF, but if you google the following exactly within these "quotes" (without them though on google) "nintendo power final fantasy guide" the first link goes to a site called emuparadise, and it's a direct link to the original 1990~ Nintendo Power Volume 17 which was a cover to cover guide for the NES release of Final Fantasy. Classic style all the way with every single square inch of every map in the game photographed and notated page to page broken into over 10 chapters of the game. All maps, all gear, spells, items, prices on it all, the monsters and bosses and their stats, attacks, and weaknesses.
This is THE guide to use above all else for the NES as it was made for it and is far easier to follow than some sketchy typed up FAQ file. I own the magazine and it's required reading for the crusty old gem.
Mind you the post above, that's a scan of the nearly 90 page instruction manual and it's super helpful too and has part of the game as a guide in there as a travelers handbook. Insane side note, if you ever find that manual online in TXT format, I'm the crazy SOB in the 90s who typed that entire thing out on one very boring weekend I had and needed something to do.