Maximum capacity hard disk in Optiplex 9010

I couldn't check specifics of your system, because you didn't specify if it is Small Form Factor, Ultra Small Form Factor, or Mini-Tower. So, I'll give general advice for Optiplex family:

If your system is UEFI with GPT disk, you can use drives up to 4 TB in size.
If the system is legacy BIOS with MBR disk, you can use drives up to 2 TB in size.

Dell's maximum memory and storage specifications are published at the time of system design, based on what they tested. It's not a limitation, so don't take it as gospel. Technology evolves, and often larger RAM sticks and larger drives become available after Dell publishes the specs, and Dell does not generally go back to revise the maximum specs. So, Dell's specs should not be interpreted as limitations or maximums.

Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard. (Repeatedly touching a metal case part is not sufficient mitigation with modern components.)

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@Togomi wrote:

Regarding to UEFI with GPT or legacy BIOS with MBR disk, I don't know.

How can I know that?

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You may use Windows utility Disk Management or use command line. Details here: How to Check if a Disk Uses GPT or MBR, and Convert Between the Two (howtogeek.com)

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@Togomi wrote:

I was checking and I have BIOS with MBR.

So, only 2 Tb.

What happends if I put a 4 Tb HDD? Won't it work or only use 2 of 4 Tb

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I believe you would be able to use 2 TB, but the rest of the capacity would be unusable in MBR.