Getting audited for the first time and last hopefully

I have basic general questions about my audit. I am a w2 sales person full

time and also have a start up premium travel company so I travel about 12 weeks a year and fly around the world staying in hotels and creating contracts with hotels, airlines, and tours for my customers. I want to know how to file an audit extension and what documents to include to the irs audit. I have all my flight receipts and hotel receipts. A lot of my business is done in Thailand where there's no receipts and everything is paid with cash so I don't know how to submit for meals in that case. Any advice would be awesome. Tax audit app wants to charge me $1100 to represent me for the audit. I'm not sure if that's a good idea or if I can easily do this myself.