Recall that the Force #vecF# experienced by a charged particle of charge #q# moving with velocity #vec v# in a magnetic field #vecB# is given by the relation

#vecF=q(vecvxxvecB)#

We also know that

velocity #vecv="displacememt"/"time"#

If the charge moves through distance #=#length #vecL# in time #t#

#vecv=vecL/t#. Inserting in the force equation we obtain

#vecF=q(vecL/txxvecB)#

Rearranging scalar quantities we get

#vecF=q/t(vecLxxvecB)#

#=>vecF=I(vecLxxvecB)#, where #q/t=I# is the current flowing in the wire.

You may use the expression #vecF=|vecL|(vecIxxvecB)# knowing well that the direction of #vecI and vecL# is same.

However, we must appreciate that direction of #vecL# defines the direction of #vecI#. Perhaps and not vice versa.