As others have already said, one of your columns datatypes in the source table is larger than your destination columns.
A simple solution is to simply turn off the warning and allow truncation to take place. So, if you're receiving this error but you are sure it is acceptable for data in your old database/table to be truncated (cut to size) you can simply do the following;
SET ANSI_WARNINGS OFF;
-- Your insert TSQL here.
SET ANSI_WARNINGS ON;
As above, always remember to turn warnings back on again afterwards. I hope this helps.