Here are the steps to achieve this automation:
Step 1:
Click on "Settings".
Step 2:
On the left side of the screen, look for "Contacts" and click on it.
Step 3:
Look for the contact you would like to update and once you find it, click on the "Edit" button.
Step 4:
Make sure you have under the Account Type "Supplier" selected and press the "Update" button.