There are two ways ,either go with sulpher or go with silver .
Let's go with sulpher
Moles of sulphur
[tex]\\ \rm\rightarrowtail \dfrac{350}{32(8)}[/tex]
[tex]\\ \rm\rightarrowtail \dfrac{350}{256}[/tex]
[tex]\\ \rm\rightarrowtail 1.36mol[/tex]
1 mol of sulphur forms 8mol silver sulphide.
Moles of silver sulphide
[tex]\\ \rm\rightarrowtail 1.36(8)[/tex]
[tex]\\ \rm\rightarrowtail 10.88mol[/tex]
Mass of Ag_2S