What is the correct dosage for amoxicillin to treat UTI in adults?

Depends! Correct Amoxicillin dose for any infection depends upon sensitivity of bacteria causing infection. If bacteria is resistant to Amoxicillin or similar antibiotic, then it's a poor choice & won't work. That's why it's important to sent urine for c&s (culture & sensitivity). Btw, antibiotics like Amoxicillin only work against bacteria but not against virus which cause most common colds & sort throats.