Baking emergency! Please help with a cocoa substitution.

I am baking a chocolate cake that calls for ¾ cup of unsweetened cocoa. Since I always have cocoa on hand, I didn’t buy any when planning to make this cake. Now it is Christmas Eve, the grocery store is closed, and the two mini-marts that are open don’t carry cocoa!

I do have one bag of semi-sweet chocolate chips. Can I substitute melted semi-sweet chocolate for the cocoa? How much, and do I need to alter other ingredients? This is the recipe if that helps.

The cake is for Christmas dessert tomorrow. Thanks in advance for any help and advice!