I've tried to compile that code and I got:

! terminal: >> picture
! Isolated expression.
<to be read again>
                   ;
<*> ...3u yscaled 60.09u shifted (69.85u,20.30u) ;
                                                   ;

.

system          > tex > error on line 17 in file kk.tex: terminal: >>
picture
! Isolated expression.
<to be read again>
                   ;
<*> ...3u yscaled 60.09u shifted (69.85u,20.30u) ;
                                                   ;

 ...

 7     numeric u;
 8     u:=1;
 9     textX:=87.51u;
10     textY:=96.31u;
11     pic:=thelabel.urt(btex {Test} etex scaled 1.00,(0,0));
12     draw pic shifted (textX, textY);
13     externalfigure "mill.png" xscaled 80.13u yscaled 60.09u shifted
14     (69.85u,20.30u) ;
15     \stopuseMPgraphic
16
17 >>  \useMPgraphic{gh}
18
19     \stoptext
20
<inserted text> ...re.mp ; fi ; ;;;;]===], false)}

\processMPgraphic ...e ;\!!es , \MPaskedfigure )}}
                                                  \egroup \placeMPgraphic
\d...
\handleuseMPgraphic ...hics \processMPgraphic {#3}
                                                  \endgroup
\douseMPgraphic ...{\@@MPG \currentMPgraphicname }
                                                  \empty \endMPgraphicgroup
<to be read again>

l.17 \useMPgraphic{gh}

-------------

I have no idea of what to do. Any ideas? Thanks