Transition from Schedule C to LLC

Hello,

I have had a business since 2018. In 2018 and 2019, it was a Schedule C business. January 1, 2020, we converted it to a Multi-partner LLC. I have carryover home office expenses from 2018 and 2019. Can I apply those to the LLC in 2020? Also, what do I use for the "Date business began" in TurboTax... 2018 or 1/1/20?