I have a table with one of the column [last seen] nvarchar datatype and data imported from .csv file. Data in the [last seen] column is in Unix Timestamp in MilliSecs format 
I need to convert it from unix timestamp to datetime format.
Tried changing the datatype of the column from nvarchar to datetime and getting below error:
- Unable to modify table. Conversion failed when converting date and/or time from character string.
Can someone please give an idea\solution to fix this issue. Thanks in advance.