You need a RS-232 to to TTL level shifter, the MAX232 is commonly used. You can buy the required DB9 and a MAX232 on a board for a $1 from China. Only issue is they’re usually counterfeit parts although they reportedly work.
The CH340G is solid part, used tons of them without issue. What OS? Post a picture of the module you have, i probably have one I can test or comment on.