I'm trying to figure out from a migration perspective how much of an issue this is/was. But I can't get any total figures on a quick google search, unlike say for Syria. This may well be because of the longer time span involved, as well as the expansion/changes of the EU in the same period. So, is there even a ballpark estimate for Afghan migration to present-day territory EU in the past 25 years? (You may include the UK area, if that makes it any easier to come up with an answer.)
N.B. I found some [yearly] numbers for Greece, in the 2001-2012 period, which are sourced from FRA, but without citing a particular FRA document... The numbers varied significantly from some 757 in 2011 (min) to 15,314 (in 2008, max). It's pretty hard to extrapolate Europe-wide from these though...