Ref. No. 1786/43-1533
In the name of Allah the most Gracious the most Merciful
The answer to your question is as follows:
You did not specify which serials make people convert to Islam. However, in this regard, it should be kept in mind that only the goal and the result should not be good, but also the steps to achieve this goal should be good and in accordance with Shariah. Serials usually contain a lot of obscene and prohibited materials. So watching such serials should be avoided according to shari'ah.
And Allah knows best
Darul Ifta
Darul Uloom Waqf Deoband