The issue is that the Drive is 26 years old. That is even assuming it still functions. And you can get it to work.
The Dell M6400 uses SATA connections. The drive is either IDE or SCSI (the model is produced in both variants). Unfortunately, that's going to be a problem because while you can get converters to connect SATA drives to IDE connections, the same cannot be said going the other way.
The drive is only 340MB, so it's presumably not going to be sufficient to replace whatever drive is already in the system unless you severely downgrade the software and use an older Operating System, which is going to give you trouble with driver software. Most Laptops can have a Optical bay converted to an additional HDD Bay- but again the models for the M6400 appear to all be for SATA Drives.
If you must use t he drive, you might find a 2.5" IDE Enclosure to use it as an external drive.
