def convert_sigmav(sv, target):
    """Changes the units of <sigma v>.

    Parameters
    ----------
    sv : float
        Cross section in units of MeV^-2 or cm^3 / s.
    target : string
        Units to convert to. Must be "MeV^-2" or "cm^3/s" -- whichever units sv
        is NOT in.

    Returns
    -------
    sv : float
        sv converted to be in the target units.
    """
    hbar2_c3 = 30000000000.0 ** 3 * 6.58e-22 ** 2
    if target == 'cm^3 / s':
        return sv * hbar2_c3
    elif target == 'MeV^-2':
        return sv / hbar2_c3
