URGENT! Please help... my furnace started blowing nothing but cold air yesterday. I tried locating the filter but couldn't find it anywhere. If you can help me please respond!

Hope you got heat by now!:)
If it's the newer type furnaces all electronically controlled, the average handyman is at a loss and your best bet is to find an "expert!"
Sorry, I'm sure that's not what you wanted to hear!

I have asked to have your question moved to Heating and Air Conditioning. Some of the people there are very good and have helped many home owners like you. Sounds to me like the high limit switch is tripping. You are on the right track with the filters. They are often in the return duct next to the blower housing. If you find and replace the filters, and still have the problem, check the high limit switch itself.

Read the sticky in the heating forum, https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html It is a great resource that must have taken a good man a long time to prepare.