Getting error "String or binary data would be truncated" even for 'text' data type
You are trying to put data into a column that is not wide enough for it, as the message suggets.

IIRC Postgre's text columns are open sized much like SQL Server's [N]VARCHAR(MAX) so I suspect there are some long values in there and the target column(s) in your table in SQL Server is a more limited character type (VARCHAR(50) or some such.

That is only a guess though. We can't be any more speicif without much more detail from you. What are the table definitions in Postgres and SQL Server? What tool(s) are you using for to migrate the data (SSIS, plain SQL, something else?)?