Transform minimum phase FIR into linear phase FIR
It is generally impossible to transform a given minimum-phase FIR system into a linear phase FIR system with the same magnitude response. There is one special case for which this is possible, and that is if the zeros of the minimum phase system inside the unit circle haven even multiplicity. Because in that case you can, for each zero location, mirror half of the multiple zeros across the unit circle, which gives you a linear phase filter without changing the magnitude. But that's of course a quite artificial situation, so in general there's no way to obtain a linear phase filter from a minimum phase filter without changing the magnitude.

A way to transform a minimum-phase FIR system into a linear-phase FIR system with a squared magnitude is by simply doubling all zeros on the unit circle, and for each zero inside the unit circle adding a mirrored zero outside the unit circle. If $H(z)$ is a given $N^{th}$ order causal minimum-phase transfer function, the corresponding linear phase transfer function is given by

$$G(z)=H(z)H(1/z^*)z^{-N}\tag{1}$$

Note that the number of coefficients is (approximately) doubled and that

$$|G(e^{j\omega})|=|H(e^{j\omega})|^2\tag{2}$$