i try to import obj model in blender 2.9 but it is very small and i just can’t resize/scale it in any known way but when i view the model in Microsoft 3d viewer i can see it just fine.
Sorry, but we have no way of knowing what you know. Your screenshots provide no info so we can’t tell if you’ve actually imported anything or if you’re just taking a screenshot of a random origin. So we can not tell if this is a scale issue.
Try making your screenshots more helpful to those who want to help: e.g. display relevant info (in this case, the object-info panel showing us the dimensions of the object would have been a lot more helpful than the tool-tab), and, even more helpful, select the imported object and do a View->Frame Selected. Thanks.