Mixed Model Analysis SPSS

#1
Hello All,

I have a data set which I am trying to find out what is the best way to go about analyzing. I have been asking around and was advised that mixed model is the best way to go.

Basically, this is a brief explaination of my data set.
I am trying to see the efficacy of Drug X on tumor bearing mice.
I have tumor volume measurements over a few time points from 3 groups of 6 mice each, control, 50mg/kg and 100mg/kg dose.

I would like to see if there is a significant difference between 50mg/kg vs control and 100mg/kg vs control.

How would I do the mixed model analysis in SPSS?

I am not very good with stats and any help is greatly appreciated.
I have attached an example SPSS dataset to help visualize better.

Thank you very much for your time!