Volume average of SAR value

How can
I calculate the volume average of SAR value in a sphere for example?

Use the SAR Statistics algorithm (there is a checkbox that enables psSAR values too). You will get plenty of SAR-related data for every object in your simulation.

Thank you so much for your reply. And do I need to tick the checkbox Normalized Frequency-Domain Results in overall field and change the target value to the target value which could be calculated like tutorial

Yes, you should in principle always normalize the fields before computing SAR.
SAR values are "dimensional" quantities* and, as such, they only make sense in a specific "context of use": geometrical setup, power emitted by a device, etc... I can't say whether you should be using the same target value as in tutorial, as that really depends on your application.

*The SAR is computed from the electric field, the intensity of which depends on the power radiated by the system, which itself depends on the input power.

In some tutorials the fields are normalized to 1 W of target value for SAR in and psSAR for, Is that fine If I do that for the other simulations
or I need to normalize the fields to a target value that could be calculated using rms E-field and the formula in tutorial

Again, it really depends on your application (i.e. what you are computing the SAR for). For regulatory submissions, normalization will be dictated by the so-called "conditions of use" or by some standards.

In any case, I would suggest to choose normalization settings which are as close as possible to realistic scenarios and to always report the chosen power (or fields) target values along with the SAR values.

Thank you for your explanation.
the normalization is needed to be chosen just for calculating SAR value or for other quantities such as B-field it is needed as well?
To find the exact target value, the rms E-field at the wire location (which is considered in the middle of the wire in tutorial for a straight wire could be calculated easily. But I'm wondering for a bent wire, which position I need to consider to calculate the rms E field?

Normalization applies to the whole sensor, so all quantities (E, H, B, SAR, etc...) will be scaled accordingly.

As for which position you need to consider for the rms E field... well, that's up to you. Different normalization will lead to different SAR values.

Actually for a bent wire when I extract the rms E field in a position and then calculate the target value, then I use this value to double check if it is correct, but I don't get 1 v/m for the E field at the same position which rms-E field is extracted. Does it mean I'm doing something wrong?

To get a meaningful answer to this kind of question, you would need to provide more detailed information: such as screenshots (you can copy/paste images into your posts), formula, numbers, etc...