Broken rear leg

Bighammerfan

Whilst packing our caravan up after a great weekend yesterday I was winding the legs up and as I did the rear left hand side leg there was a bang and the back of the van slumped down. Looking underneath I could see the part that moves along the threaded
bar had snapped. I can see the bit thats broken but was wondering if anyone could point me in the direction of a tutorial on how to change it for a new one. Also is there any way I can find out the size as its in storage and like a fool I forgot to measure
it before we left. I assume its the AL-KO corner steady leg worm I need in either 16mm or 20mm.

 

Alan