What is a task type? I have an unlabeled dataset: 500 X-rays of seeds in husk. In each image there are different number of seeds, for instance, from $10$ to $50$.

A seed has some features. The main features are a seeds' square and a husks' square in pixels. I need to calculate the these features ratio.
I am looking for an objects recognize algorithm.
My problem is: I don't know what is a task type.

The dataset is unlabeled and I can use unsupervised learning and identify a similarity in groups (clustering task). Or I should to label data and use supervised learning and identify a real values (regression task)?
Question What is a task type?
Literature

The Plant Pathology 2020 challenge dataset to classify foliar disease of apples
Exploring Survival on the Titanic
This is likely to be a challenging task, and if you're not familiar with image classification, I suspect it may be beyond what you can reasonably do right now.
I would suggest you investigate classical image processing techniques.  You might try applying morphological operators, such as closing (dilation followed by erosion) or opening followed by thresholding.  You may need to experiment.  If you search on Stack Overflow and Signal Processing sites, you'll find many examples.
See also blob detection and watershed segmentation.