The answer to how many IOPS for a 15K 146GB SAS HDD is it depends.
For example there are some general numbers of around 200+/- IOPS for that type of drive doing about 4K+/- IO size reads. The manufactuers site among others will give you a general number which will either be an average, or for a specfic IO size which might be different than the IOPS you will be doing.
You might get higher with smaller IO size on sequential reads vs. random writes which will also depend on what the HDD is attached to. For example are you going to attach the HDD to a storage system or appliance with RAID and caching?
Are you going to attach the HDD to a PCIe RAID card?
Or are you simply going to put the HDD into a server or workstation and use as a drive without any RAID or performance acceleration.
The reason I mention using a RAID adapter or other performance accelerator or storage system is that you may get more performance being able to tap into the HDDs full potential.
So what are you going to use the HDD for, and how will it be configured?
Here is some related material around HDDs and performance.