We started a lawn mower repair business but are using tools that we personally had for the business. How do we document those tools now for business use and how much do we allocate as an asset for tools and equipment?

Generally, use something like Turbo Tax. It asks the year the tools were purchased and the amount. Then it asks when they were placed into service and what percentage of the usage is dedicated to business applications and what percentage to personal use.
Hope that helps.

1. Estimate the Value of the mower at the date you moved it in as an asset of the business.

Journal entry :-

debit equipment account xxxx
credit loan owners xxxx

transferring lawn mower into business.