Correct

铁杵磨成针

/ tiě chǔ mó chéng zhēn / 
Strokes

Example

Definition

an iron pestle can be ground down to a needle—steady/persevering efforts can work miracles; perseverance will prevail

1
Zhǐyào
只要
gōngfu
功夫
shēn
深
  
,
tiěchǔ
铁杵
móchéngzhēn
磨成针
  
。

So long as you work hard enough (at it), even an iron pestle can be ground down to a needle. / Persistence means victory.