Forgot my unlock pattern how can I reset it - Ematic 7" Touch Screen Tablet

There are lots of things to try before getting drastic...
See this:

Recover Android Device in case of Forgot password pattern unlock an...

You could try the reset button on the back. It's not really a visible button but a hole into which you can poke a paper clip.

Turn on the device until it gets to the pattern lock screen and
then use a paperclip to gently press the reset button in the hole in the back until you feel it click.

It should reboot but it will probably STILL require the pattern.
(Most do, only a few don't)

If it does indeed still require the pattern you'll have to go with the factory reset option which will wipe all your data and restore it to the same condition it was when it first arrived. This is drastic but there's just no way around a forgotten PIN or Pattern other than this. They do it that way to protect lost devices from having all your password protected sites like GMail etc. being accessed and taken over by somebody else.

The way to do a factory reset on an Android tablet is turn it off and then turn it back on by holding down both the power button and the volume(-) button at the same time and keep holding them for as long as 30 seconds until you see some green writing on the screen. This green writing is list of options among which you will see a Wipe Data/Factory Restore option (or similarly worded) . Use the volume(+) button to scroll to the Wipe Data Factory Restore option. Once it's selected, push the power button once to engage. On most Android devices, you will then get another screen with writing that is a list of no no no no and one line with a proceed with the reset option. Scroll to it using the volume (+) button and select it using one push of the power button. The unit should then either turn off or go to another screen where you can turn it off using the power button.

When it's off, give it several seconds and then push and hold the power button until it boots up. You will have to go through the set up routine again and update apps you want updated and add back the apps you had installed from the Google Store. You will have to again add your password for the wi-fi you are using before you may do any updates because the password will have been wiped, too.

Good Luck and I'd recommend using a PIN instead of a pattern and WRITE IT DOWN so it can't be forgotten.