First it is important ot remember the folllowing:
1) "hm" is hectometre.
2) "dm" is decimetre.
In order to solve the exercise you also need to remember that, by definition:
[tex]1\text{ hm}=\text{ 1,000 dm}[/tex]Knowing the above, you can make the conversion from hectometre (hd) to decimetre as following:
[tex](3.0035hm)(\frac{1,000dm}{1hm})=3003.5\text{ dm}[/tex]Therefore, you get that the answer for the question is:
[tex]3.0035hm=3003.5dm[/tex]