The only way to transfer from 3DS to Switch and beyond is to use HOME.
Transfer everything to Gen7, either legitimately or by save editors like PKHeX, then use HOME to transfer into the Switch era, and trade manually.
If you are unable to use HOME from the 3DS, then you are unable to bring things forward in a HOME-compatible future-proof way. Injecting manually to a hacked Switch will lack a tracker, and the Pokemon will be unable to be moved into HOME and other games.