See if this is your part:
https://www.searspartsdirect.com/product/38q218l77n-0006-147/id-1000111068?sid=pla:ggl:1000111068:pla-293946777986&gclid=Cj0KCQjwhr2FBhDbARIsACjwLo37-GWyjvBJg9GSpd-tZqDCRggQ6UDK1D5z6oqgMa0_VIchR8PKyyAaAgsCEALw_wcB
If not do a search for this:
https://www.google.com/search?q=control+board+%26+%22Lifespan+TR3000%22+l+Treadmill&client=safari&rls=en&biw=1656&bih=994&tbm=shop&sxsrf=ALeKk03CLZFOVO_5SvFHk7y8wxVoaatmjw%3A1622147077622&ei=BQCwYO7AJcf0tAaRj4_4Cg&oq=control+board+%26+%22Lifespan+TR3000%22+l+Treadmill&gs_lcp=Cgtwcm9kdWN0cy1jYxAMMgQIIxAnUMOSAlj4wQJgzNgCaABwAHgAgAGOAYgBnwKSAQMyLjGYAQCgAQHAAQE&sclient=products-cc&ved=0ahUKEwiu19bi2OrwAhVHOs0KHZHHA68Q4dUDCAs