I agree with Bitter Old Man. If they are both single tenant, NNN lease properties, most of the value is in the lease rate, term remaining and creditworthiness of the entity on the lease - all of which can be tied to a market cap rate.
These type of properties are in high demand right now, and a broker can easily help you place a value on the sites.
Full disclosure - I am a broker in DFW. I do not specialize in NNN investment sales, but I am happy to answer questions and point you in the direction of someone who can help you further.