The <l7:Pkcs12Data> is the data of p12 file, but it's base64 encoded, just base64 decode and save it as p12 file.
I tested on my linux box,
echo <copy and paste l7:Pkcs12Data> | base64 -d > test.p12
and verified by openssl,
openssl pkcs12 -info -in test.p12
it returns the detail of the private key successfully.