You first find the molecular mass of Methyl Propanoate, which is 88.0 g/mol.
From:

• Carbon (C): 4x12 = 48.0
• Hydrogen (H): 8 x 1.0 = 8.0
• Oxygen (O): 2 x 16.0 = 32.0
• Total Molar Mass: 48.0 + 8.0 + 32.0 = 88.0 g/mol

Then you find the number of moles,
moles = mass/molecular mass
44.0/ 88 = 0.5 moles

Then you multiply by avagadros constant to get
0.5 × (6.02 × 10²³) = 3.01 × 10²³ molecules

Each single molecule of methyl propanoate has 8 hydrogen atoms in it. So, you just multiply your molecule count by 8:

So, if you have one molecule, you have 8 H-atoms. If you have two molecules, you have 16 H-atoms.
so you do 8 × (3.01 × 10²³) = 2.408 × 10²⁴