I have a little trouble understanding you. It would help if you had DDL, sample data and expected output. In the absence of that, see if this pattern works for you:
SELECT [other columns], Paid1 FROM dbo.MyTable WHERE Paid1 IS NOT NULL
UNION ALL
SELECT [other columns], Paid2 FROM dbo.MyTable WHERE Paid2 IS NOT NULL
UNION ALL
SELECT [other columns], Paid3 FROM dbo.MyTable WHERE Paid3 IS NOT NULL