Hi, could any one help me with the following two issues?

First, my id variable values start with 001, 002,... 011, 012, ... 099... and they are all coded as "string".
I thought I should convert them into "numeric" (please say no if this is not what I am supposed to do) and once I converted them, all zeros are gone.
How can I keep those zeros even when I convert them as numeric and is it really necessary or desirable to keep those zeros (since they are original id, so I think I should keep them)?

And second question is:
If some of group id variables start with alphabet (e.g. this household belongs to G35) as "string" variables, then can I just keep them as string or should I convert them something else that should work in Stata?

Sorry for bombarding many questions.

Thanks.