listing you exact Dell model would be helpful to give you an answer.
Fit - no problem, but the question is does it have the SATA ports and if yes, what gen. If it has SCSI, best hope it has gen 2. so there is no point in fancy SSD as the SATA 2 is limited to 300MB/s and SATA 1 is just 150. So you can safely peak the cheapest SSD.