Did you download Sumatra from official Sumatra website?
If not, we can't help you because we didn't create the software you're using.
There are 2 versions of Sumatra: an installer and a portable version (zipped executable).
If you're using zipped executable, the only thing you need to do is to delete SumatraPDF.exe.
If you installed SumatraPDF by running official installer, you uninstall it like every other application.
On Windows 10:
Apps
SumatraPDF
on the list, click it and press Uninstall
button:What if you still have questions? You can use the forums to ask for additional help.
However, in order for someone to help you, you need to provide the following information: