If $\overline{A}\text{ and }\overline{B}$ are two vectors then a new vector parallel to $\overrightarrow{\mathrm{A}}$ having the magnitude of $\overrightarrow{\mathrm{B}}$ is

$\hat{\mathrm{A}}$ is unit vector in the direction of $\overrightarrow{\mathrm{A}}$.

B is the magnitude.

on multiplying both we get the required vector.