How to use api response string

How do you go about reformatting or getting values from an api response value?

I used the Lead Convert method to convert a crm lead to a potential and create a contact.

I get the following response:

{"responseCode":"200","responseText":" \n710378000007272009<\/Contact>710378000007272011<\/Potential><\/success>\n"}

How can I use this response?

I know that 710378000007272009 is the contact ID

I know that 710378000007272011 is the potential ID

But im not sure how to get these values out of the string since it's kind of a cluster.

It seems this is a map but the keys are not obvious / don't exist from what i understand.

Please help, thanks