If formula issue

1. You don't need the spaces between the quotation marks. A cell with a "blank space" in it is not an empty cell. A space is an actual character.
2. If B2 is empty then just enter 3 into C2, no need for the addition.
3. You need to add an action for the False condition of the IF formula:

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Notice the last set of quotation marks will leave the cell empty if the conditions are not met; otherwise, Excel will put FALSE in the cell.