The problem provides you with grams of titanium(IV) oxide,
This means that you're looking for a conversion factor that can take you from grams to moles and vice versa.
For any compound, this conversion factor is called the molar mass. The molar mass tells you the mass of exactly one mole of a given compound.
In you case, you can use the molar mass of titanium(IV) oxide, which is equal to
So, a molar mass of
#200.0 color(red)(cancel(color(black)("g"))) * overbrace("1 mole TiO"_2/(79.866color(red)(cancel(color(black)("g")))))^(color(purple)("molar mass of TiO"_2)) = color(green)(|bar(ul(color(white)(a/a)"2.504 moles TiO"_2color(white)(a/a)|)))#
The answer is rounded to four sig figs, the number of sig figs you have for the mass of titanium(IV) oxide.