You appear to have a violation of normal form by storing more than one piece of data in a single column. I think, ideally, you would want a table that had each piece of information stored in it's own column.

Col1, Col2, Col3

AL003, 1, P1

CC013, 1, P01

Etc...

The application that uses this data could then either access it through a stored procedure or view:

CREATE VIEW dbo.something

AS

SELECT Col1 + '/' + Col2 + '/' + Col3

FROM table

GO

And the results of querying dbo.something would look like...

AL003/1/P1

CC013/1/P01

Another option would be to create a computed column on the table that would concatenate the three data.

But to answer your question, I think you want an update that looks something like this?

UPDATE table

SET columnname=PARSENAME(replace(columnname,'/','.'),3)

+ '/'

+ PARSENAME(replace(columnname,'/','.'),2)

+ '/'

+ REPLACE(PARSENAME(replace(columnname,'/','.'),1), 'P', 'L')

It's messy and that is an artifact of trying to tease out the different pieces of data stored in the column.