Answer:
MnO > Ni₂O₃ > ZnO> Cu₂O > V₂O₃
Explanation:
To answer this question you must know the smallest ion with the highest charge will be the most acidic. For the oxides:
ZnO: Charge Zn⁺²; radium: 74pm
Ni₂O₃: Charge Ni⁺³; radium: 74pm
V₂O₃: Charge V⁺³; radium: 78pm
Cu₂O: Charge Cu⁺¹; radium: 77pm
MnO: Charge Mn⁺²; radium: 70pm
As the smallest ion is Mn⁺², MnO will be the most acidic, then Ni₂O₃ because is the samllest ion with ZnO but has a highest charge, then Cu₂O and V₂O₃
The order is:
MnO > Ni₂O₃ > ZnO> Cu₂O > V₂O₃
I hope it helps!