If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness. (NIV)

If we [freely] admit that we have sinned and confess our sins, He is faithful and just (true to His own nature and promises) and will forgive our sins [dismiss our lawlessness] and [continuously] cleanse us from all unrighteousness [everything not in conformity to His will in purpose, thought, and action]. (AMP)

If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. (KJV)