Updating a sharepoint number column with previous total + 1

I'm trying to update a sharepoint number column when a form is submitted. The sharepoint list keeps track of total number of items in another list. I can't find any information about how to update the number column every time a form is submitted. Currently, I have the code.

ForAll( IntakeFormCartFinal, Update(Assets, {ID: ID, 'Total Count': + 1}))

As far as I can tell, everything is fine until the variable to add 1 to the 'total count' column. I don't know how to get that as a variable to do any addition/subtraction. Is this possible through powerapps or would I need to use power automate in some form?