how do I determine FMV for properties inherited in Oct. 2020 - then sold in 2021?

3 condo/apartments - all investment properties - supposed to use date inherited (October 2020) to determine value of each..

 

planning to use tax assessed value for 2021 or possibly an average of 2019, 2020, 2021 - or maybe just average of 2020-21

 

is there a best way to determine FMV? 

 

title transferred at sale to new buyers - never assumed ownership, HOA dues, mortgage payments, etc. at the time inherited.

 

sales were in May, July, and November 2021 - received Form 1099-S for each property - no K-1's