Hi @Akito,
thanks a lot for your comments. 
You´re perfectly right in assuming that. 
That´s exactly the reason why I´d like to use my old SIM card as long as possible.
O.K., that´s really good advice. Thanks.
But as @hamaer said:
it looks like I may use my present SIM card in the Huawei E3372 stick just as it is.
The size seems to be the correct one (2ff).
Many greetings.
Rosika 