What motion can one bring into court to counteract a motion to dismiss?

-I recently filed a claim for unemployment. The claim was processed but I was disqualified from receiving benefits for sixteen weeks. I appealed the decision and was supposed to file a brief in 20 days and send a copy to all parties. I did that, but unfortunately, I didn't mail the letters. I brought them myself to the department of Labor. Now they claimed that they received it and asked the court to dismiss my claim because I don't follow the rules. I have a stamped p[age from my brief that they received the brief in their office. My question is: Since I have the proof that they received the brief through the date-stamp attached on the copy that I have in my possession. What kind of motion can I bring into the court to counteract what they ask for. they ask for a motion to dismiss with prejudice

Please adviceFirst, you need to find out ASAP how long you have to respond to the motion to dismiss. Second, file a Memorandum in Opposition to the MTD. It should recite that they received the brief/papers/letters/or whatever else was supposedly lacking and you should attach the file stamped copy as your proof. Be sure that you end with a notarized signature of yourself.