It depends on your converters, but 0VU could be anywhere from -12 to -18dBFS.
That is to say, 0VU is zero "volume units", which is the passed-down-from-times-of-old term for the zero setting on any meter, whether it is a VU meter or not. So if your converter uses a "pro" +4dBu level, then 0VU=+4dBu. However, 0dBFS will be set somewhere north of that, to provide headroom. +19dBu is probably a rough average, thus 0VU would be -15dBFS in that case.