Pop a google search for pokemon scarlet violet trade discord. Highly reccomend joining. Theres a channel there to post and ask for trades. Used it going for my pokedex completion at launch.

Not every pokemon is availble in S/V, so you might need to look up a list of whats possible.

You can also use the pokemon home app to trade pver pokemon from the DS and Switch games.

Internet acces is needed for all the above however.