How to convert smiles (.smi) to pickle (.pkl)

I converted my .smi files to .pkl but I am getting this error when I load the picke file. I think the way I converted it is wrong hence the error: in <module>
    qm9_smiles = pkl.load(f)

UnpicklingError: invalid load key, '['.

Here is a snippet of code I used for the conversion:

with open(out_path, "wb") as f:
    pkl.dump(file_path, f, protocol=pkl.HIGHEST_PROTOCOL)

Any suggestions for me is welcome. Thank you in advance