No records to document adjustments to basis

I am planning to sell a home I’ve owned for more than 30 years.  For a number of those years when I was living overseas, more than 20 years ago, I rented the house to tenants and claimed depreciation.  I do not have records to document how much depreciation was claimed during those years.  Also, I did a major renovation to the house about 15 years ago but can’t find the records to document those costs.  How can I figure the basis for this asset to calculate the taxable gain?  Thank you.