Here's the TurboTax FAQ that answers the "how many" question:
https://ttlc.intuit.com/questions/1899287-how-many-stock-transactions-can-turbotax-online-handle
As to the "cost basis" question, I assume that the broker is not reporting basis to you, perhaps not even providing a 1099-B. In that case the generalized and correct answer here is: that information has to come from your own records. As an "investor" you are, ultimately, the one responsible for tracking your trading activities and determining the correct basis to use.
In your case then I'd expect you'd have to go through your old statements from the broker or look at historical transactions at the broker's online site and determine the basis to use for each security sold. If the transactions occurred in a foreign currency then each activity - each purchase, each sale - needs to be translated into US Dollars.
https://www.irs.gov/individuals/international-taxpayers/foreign-currency-and-currency-exchange-rates
Tom Young
