I need help.
How I can to install CH341 USB Driver ?
I am using linux Mint 19 - Kernel 4.15.0-20-generic.
I want to access console port in a switch and router, but I can not, because I dont have drive for CH341.
Can you help me?

This is a subforum for Slackware installation issues. You would want to post this in a Mint forum for help with your distro.

But according to research, it seems like that driver has been in the kernel for quite a few years already (I checked back and it existed in the 3.9.x kernel, which was released 6 years ago).

This Q has apparently now been moved into Linux Mint territory, so lessee here;

The driver (although apparently included in kernel code) is available from the Chinese manufacturer of your USB-Serial chip, the CH341 in several package variants.
It is very inexpensive, so showing up in many adapters; mine came from eBay for $10US delivered, as a ham radio programmer interface.
Use the Archive Manager to extract your downloaded CH341SER_LINUX.ZIP and in a terminal session, cd {the folder you extracted it to}, then
make && sudo make,
sudo insmod ch34x.ko
reboot
and Bob's your uncle!
Hope that helped!