Thanks for the answer. Do I have to use fMRI images or just conventional MRI images

Thanks@Nicolas Clairis

It is a bit unclear what you mean by fMRI images versus conventional MRI images. By fMRI images, you might mean EPI images, SPM and other similar software packages can read and display any MRI images saved in the NIFTI (.nii) format. The type of contrast does not matter, as far as reading the files and displaying the images. However, if you simply want to display images, SPM is not really the best choice.

Possibly by fMRI images, you mean NIFTI files, and by conventional MRI images, you mean DICOM images. Typically MRI scanners save their data in the DICOM format. SPM does not accept data in DICOM format, but SPM has a tool for converting DICOM files to NIFTI files. Personally, I prefer to use dcm2niix (https://github.com/rordenlab/dcm2niix) for converting to NIFTI files. Most fMRI analysis packages use NIFTI files, so if you are doing fMRI, you will need to convert DICOM data to NIFTI.

As for viewing images, MRIcron that Nicolas mentioned is good for viewing NIFTI files, but it can't read DICOM files. Also, but MRIcron is no longer under development. It's replacement MRIcroGL (https://www.nitrc.org/projects/mricrogl) can read both NIFTI and DICOM formats, as well as a number of other formats. There are also many other good (& free) viewers for both NIFTI and DICOM data, a simple google search will turn up a long list.