Thank you for the opportunity to help you with your question!
If compounded annually then amount = 1000 (1+8/100)^18 = 1000×(26/25)^18 . If compounded semianually then amount = $1000 (1+8/200)^36 and if compounded quarterly then amount = $1000 (1+8/400)^72. Hope you can calculate the amounts. If not able? Let me know.
Please let me know if you need any clarification. I'm always happy to answer your questions.