I think that your dataset is too small but you can find a starting tutorial at:

  
      

      Medium – 5 Jun 20
  

  
    

Classification of Brain MRI as Tumor/Non Tumor 2

  Learn to train and apply a simple CNN to differentiate between an MRI with a Tumor and an MRI without one.

  
    Reading time: 8 min read
  

  

  
    
    
  

  


If you want to explore segmentation I suggest to take a look at the annual BraTS challenge.
Here you can find the announce of some of the top results in the 2021 challenge:

  
      

      NVIDIA Developer Blog – 30 Sep 21
  

  
    

NVIDIA Data Scientists Take Top Spots in MICCAI 2021 Brain Tumor Segmentation... 2

  NVIDIA data scientists took three of the top spots in a brain tumor segmentation challenge validation phase at the prestigious MICCAI 2021.