I am not familiar with .trj format, but since you have Amber, the easiest thing to do would be to simply convert the mdcrd trajectory into one (or more, if need be) pdb file(s), as curves+ can read pdb format.

unless I am mistaken, they are both amber Netcdf trajectory formats.. so perhaps changing the file name from .mdcrd or .crd to .trj will be sufficient???

alternatively in Amber use this command:

cpptraj -p -y input.mdcrd -x output.trj

I have checked the Ambertools manual (page 173), so these are the possible formats:

"Other currently recognized formats are pdb (PDB file), netcdf (Amber Netcdf trajectory), restart (Amber restart), ncrestart (Amber netcdf restart), mol2 (TRIPOS MOL2 format), or dcd (Charmm DCD format). "

http://ambermd.org/doc12/AmberTools12.pdf