Since no information was given on the volume of the bottle, I'll do the calculations using a #"1-L"# bottle. Moreover, you don't mention what the bottle is labeled as containing #"56.2 ppm"#. To be a little more specific, I don't know what's in the bottle to begin with.
So, I'll show you how to determine the molarity of a solution that has #"56.2 ppm"# of #"Fe"^(3+)# ions. What ppm - parts per million - means is that you have miligrams of solute in liter of solution. A #"1 ppm"# solution would mean that you have
#"1 ppm" = ("1 mg")/("1 L") = ("0.001 g")/("1000 mL"#
This means that a #"56.2 ppm"# solution will have
#"56.2 ppm" = ("56.2 mg")/("1 L") = ("0.0562 g")/("1000 mL")#
In order to determine molarity you need moles of solute per volume of solution. Since you know that you have #"0.0562 g"# of #"Fe"^(3+)# present, use iron's molar mass to determine how many moles you have
#"0.0562 g" * ("1 mole Fe"^(3+))/("55.85 g") = "0.00101 moles Fe"^(3+)#
This means that the solution's molarity is
#C = n/V = ("0.00101 moles")/("1 L") = "0.00101 mol/L" = "0.00101 M"#
The molarity of the solution is so small that you can express it as #"mmol/L"#, or #"mM"# (milimoles per liter, or milimolar)
#C = "1.01 mmol/L" = "1.01 mM"#
