Final Fantasy VII Remake has 24 Weapon Locations and Weapon Abilities. Finding all weapons and unlocking their abilities is needed for the Weapons Expert trophy.

None of the weapons are missable, you can still get all of them via Chapter Select after the story. In the equipment screen you can see which ones you've found.

There are 4 characters (Cloud, Barret, Tifa, Aerith) and 6 weapons per character. Some are automatic story unlocks, others are bought from Merchants, some are found as collectibles in purple chests. To unlock the weapon abilities you need to gain proficiency with the weapon. You do this by using the weapon exclusive ability. For example, Cloud's Buster Sword has the ability "Focused Thrust" and his Iron Blade has "Triple Slash". In the Main Menu click on "Materia & Equipment", go into Weapon Select and on the right side it shows the weapon ability and your proficiency percentage. You need 100% proficiency on all of them for the Weapons Expert trophy. Usually it's 10% per ability use (use it 10 times for 100%). You must select the ability from the Command Menu during a battle which consumes some ATB. To make it quicker, assign the ability to a specific button in Battle Settings. This way you always have the same button shortcut for the one you want to level up.

Weapons List