First, your question is a little bit imprecise, because you say
"I am having an ibis-ami file. This has more than 15 files inside".
One IBIS-AMI file can't have multiple other files inside...
But from the file extensions you list, .sp, .sp4, .ami, and .dll, it seems
that they gave you a SPICE buffer model (in the .sp files) with an
S-parameter package model (in the .s4p files) and the IBIS-AMI
parameter files (in the .ami files) and the IBIS-AMI executable models
(in the .dll files).
If you use Mentor's HyperLynx, you can most likey get your job done,
because we do support SPICE buffer models in our IBIS-AMI flow.
However, strictly speaking, IBIS-AMI models should come with the
buffer models in the IBIS [Model] format (in .ibs files).
I hope this answers your question.