Write x^3 as x*x*x

If you want it in string form you can do it like this

x^3 /. Power -> (StringRiffle[#, "*"] &@ConstantArray[#1, #2] &)

"x * x * x"

This makes use of the fact that x^3 is internally written as Power[x,3].

Since you mention another language, here's a method using CForm:

Unprotect[Power];

Power /: Format[x_Symbol^n_Integer?Positive, CForm] := SequenceForm @@ Riffle[
    ConstantArray[x, n],
    Format["*", OutputForm]
]

Protect[Power];

Example:

x^2+y^3 //CForm

x*x + y*y*y