First watch this video and follow the steps 

– Using your photo of the gel create a standard curve in Excel/numbers or graph paper of distance travelled from the well of each of the standard proteins. The ladder used was a 1 kb ladder from Invitogen Cat 10787-026
https://tools.thermofisher.com/content/sfs/manuals/1kb_plus_dnaladder_1000ug_man.pdf
– Using the standard curve calculate the size of the plasmid and the two digest fragments from your samples  
– Are the results of the plasmid what you expected – look at the plasmid map to figure this out.
– Are the two fragments the sizes you expected