How to copy strings in T-SQL that contain C-type nulls (decimal 0 in ASCII) in them?

My problem is to properly copy password hashes that are stored in the MSSQL database. I had to move one database to another server and this time I could not simply copy mdb files (what normally takes care of all the data, SPs etc), this time I used the data copy wizard instead - on ms sql 2012 ver

To my surprise all worked except one small detail, the password hashes on the source server were all 48 char long, while on the destination server those lengths were different and ended always on the char(0) - character. I know such data should be stored in binary fields but for some reason someone who created this DB used type: nvarchar(250), null - and this works on the source server, while it is trimmed on the destination server after copy operation.

I see many questions about getting rid of those char(0) characters, but what is the proper way of preserving them during copy operations in SQL server?