score:5
The simple answer is that you will require a visa, or you'll need to change your flights.
In general, Indian citizens do need a visa for all trips to/through Germany, even if you are only in transit. However there is an exception to this rule for people that hold a valid US visa which means that you do not require a visa if you are in transit, and if you will stay within the international transit area of the airport. ie, as long as you do not pass through passport control/immigration.
The problem in your case is that your flight from Munich to Frankfort is a domestic flight, and thus leaves from and arrives in the domestic part of the airport, and thus you must pass through passport control at both ends. Doing this will require a visa.
There are two types of visa that you could use for this - either a 'B' category Transit visa, which will allow you to enter and stay in the Schengen area for up to 5 days, or a 'C' category "Short Stay" visa which will allow you to stay for up to 90 days.
In practice, a better option may be to try and change your flights so that you only pass through one airport in the Schengen region. This way you can remain in the international airside area, and thus (due to you having a valid US visa) you will not require a visa for Germany/Schengen.