How Do I Check The Drain Tube On A/C To See If Its Stopped Up

Yes it does sound like either the evaporator drain tube is either plugged or it may be disconnected from the inside.
Look on the passenger side on the firewall. You should see the AC hoses going into the firewall and the heater hoses. Look straight down from there. I will not be lower than the inside of your floor boards. You should see a rubber hose that comes out and turns down towards the ground. If it is missing then you should see a hole.
If you see the hose, gently insert something in it that is flexible. Only go up just past the length of the tube that enter the fire wall... Not much more that than to see if it is clogged. If you are able to clean it out †great. If nothing comes out you might try blowing pressured air gently into it.
Let me know what you found. Just don’t pull it out

Hello Again
I found some pics for you to give you a better idea. The first pic shows the tube going through the inside of the car. Pic 2 shows the drain hole in the HVAC system that the condensation runs into. Pic 3 shows the outside of the HVAC that the tube connects onto... The sticks through the firewall below the A/C lines, usually on the passenger side (pic 1) to the engine bay area. Pic 4 and 5 shows the tube on the engine side.

I provided one other item for you..... Possible recalls on your vehicle. These are normally repaired for free. Check with the dealer service department and they can check your VIN number to their system to ensure all are repaired on your vehicle.