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There are three main methods to doing this. First, travel to new chunks. Second, delete old chunks, and make them regenerate. Third, manually place the ores in creative.
First method is travelling to new chunks. Fairly self explanatory. Easiest way to do that is with an elytra, second is getting a boat on a big ocean. Fastest way to do that is getting a dolphin on a lead, and using depth strider. More is explained here:
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Second, is delete old chunks. You could use WorldEdit or MCEdit. This will delete any builds in the chunks, and then minecraft will make the chunk like new again, so the ores will generate in it.
Third is just placing the ores in creative. You could get a friend to do it for you, so you don't know where all the ores are. You might also come up with a creative way to give yourself the minerals, such as a minigame, or other. If you don't have cheats on in your world, don't worry, as you can just open it to lan, enable cheats, and suddenly you have cheats too (temporarily)