Almost.
I was working through the math of this the other night for a project. +4dBu is a
voltage signal, referenced to 0.775 V. Thus, 4 dBu is actually 1.228V. (4 = 20*log(V/0.775); thus 0.2 = log(V/.775) and V = 0.775*(10^0.2))
-10 dBV is also a
voltage signal, but referenced to 1V. So this signal would be 316 mV (-10 = 20*log(V/1); thus -0.5 = log(V) and V = 10^-0.5 = 0.316).
Thus, the difference in
voltage would be: V = 20*log(1.228/0.316) = 11.79, or approximately 12 dB difference in signal strength.
THe short answer to your question is that almost all consoles reference their outputs to 4dBu, unless noted. Most
IEM gear will probably have a
switch on it. So just set the
switch to +4 dBu and
plug it up.