When God says that He will do something, even if it includes the following one thousand generations, He will do just as He has said, and Psalm 105 demonstrates it,
“He remembers His covenant forever, the word which He commanded, for a thousand generations, the covenant which He made with Abraham, and His oath to Isaac, and confirmed it to Jacob for a statute, to Israel as an everlasting covenant, saying,
‘To you I will give the land of Canaan as the allotment of your inheritance,‘ when they were few in number, indeed very few, and strangers in it” (Psalm 105:8-12).
Knowing the history of Israel confirms what the psalmist declared.
Therefore, if the Lord has promised to forgive you of your sins, if you believe that Jesus is Lord, and repent of your sins, and have been baptized in water, then He has forgiven you!