There are a few ways we can go about this.
Place the save from Citra into a 3DS, use Pokémon HOME to move em up, then trade over with the OP’s Switch.
Any mons that don’t exist in SWSH can be traded over via room trade on HOME.
Alternatively if the OP has a premium subscription plan, just move directly into their HOME. (HOME moving key from Bank).
Or, load up the Citra in PKHeX and drag and drop the mons from the save into SWSH.. In any case depending on how many mons, this would be a time consuming procedure...
In any case, if OP gets a HOME subscription, this will probably make things easier for anyone who is willing to help. Probably increase chances of helpers popping by too.