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IIRC, I wrote it already that OP could benefit to load all wallets with unique names in Bitcoin Core (needs maybe some preperation beforehand) and run a resync from blockchain for all loaded wallets in parallel. I'm pretty sure this is faster than dealing with every wallet one at a time.
But this optimization can be ignored if it's too complicated for newbies or less experienced users.
@Keerook: do you know if your Bitcoin Core node is pruned or has the full unpruned blockchain. The size of the default datadir for Bitcoin Core MacOS version ("~/Library/Application Support/Bitcoin/") should be in the ballpark of ~700GiB for a fully synced and unpruned Core node (don't have real numbers as I'm currently not near any of my full nodes).
As I can't fiddle with my nodes at the moment, I can't remember how to reliably query pruned or not status via command-line. (You can likely easily see it in the settings of your node in the GUI.)
This matters because a resync of a pruned node likely triggers a full re-download of the blockchain, depending from which blockheight the resync should start. If you have no clues, you'd likely start the resync from Genesis block on and then basically every pruned node would start the blockchain download from scratch like an IBD (initial blockchain download).
I work with my node mostly from the command-line and the last time I had to load a foreign or externally created wallet is quite long ago, so I'm not sure if loading a "foreign" wallet from the GUI triggers automatically a resync from block 0.
And LoyceV is very correct to point out that with such values at stake, nobody should do this with "hot" wallets on an online system. You have to be sure that the system holding the wallets with private keys is safe and free of malware and it stays so. If you don't know if your device is safe, assume it's not safe. Setup a safe device offline and keep it offline. Then proceed as LoyceV already wrote. This of course needs sufficient storage for the full Bitcoin blockchain, likely on an external drive (SSD prefered).