And to follow up what DiapDealer said, once you have done the "sudo apt-get install python3-tk", you can enter python3 in the same terminal session. Once Python has been loaded, type "import tkinter" (you'll be in the same terminal session but the prompt changes to >>> when python3 loads) and if no error message, you're good to go.
Code:
linux-6vh3:~ # python3
Python 3.7.2 (default, Dec 30 2018, 16:18:15) [GCC] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import tkinter
>>> exit()
linux-6vh3:~ #
Sample terminal session above. This is from Suse Tumbleweed running in a virtual machine so your distribution may look slightly different.