Visa questions

My husband has passed his medical and now we finally have got to the interview stage at the US embassy in London My questions are:

1) Once he receives his visa will he be given a visa number?
2) Once his visa is activated in the USA will any other documentation be sent to him or is the visa that is placed in his passport his only documentation?

The reason I ask is that he will be applying for medicare (he lived in the States for many years so he qualifies) and they require the visa number on the medicare application.