MSSQL Loop table, Populate new ID

I need to populate a column nvarchar(12) with a unique sequence starting at "PM1000000000" and increment by 1 for each row. There is no identity column to loop around which makes this problem quite challenging as most of the example I found use an identity column to loop around

I found an example, example 3 on MSDN at http://ift.tt/1KQqxpD but it doesn't show incrementing a row

Can anyone help me populate this field so that I can make this a primary key? Note: this table has 60 million rows but I'm open to any ideas at this point to just get this working