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I am sorry to hear about your lost puppies.
I cannot give exact directions, as that would be prescribing a medication without performing a physical examination. In addition, I can't vouch for why the first two puppies were lost and if deworming them is the answer.
However, to answer your question, I believe you will find the following links very useful:
The following dewormer would also be suitable for puppies:
Schedule for deworming: