Can Hair Transplant help me achieve volume/density? If no, what other treatment with 100% results can help me in this regard?

In simple terms hair transplant cannot achieve volume and density because you are only taking your existing hair and rearranging them.  There are no NEW hairs being added.  In addition, you are likely losing your existing hair.

No treatment can assure you with 100% coverage. Even if you consider a hair transplant it can be done to give an appearance of fullness or coverage to hide the hair loss. Since the reasons for hair loss among females can be due to entirely different reasons as compared to male patterned baldness, you should consider consulting your doctor for a check up.

Unfortunately, female hair loss has many different causes, and so your treatment would be based on the diagnosis for what is causing your hair loss.  To make matters more complex, female patients often have several hair loss causes!  A hair transplant is an option, but it may not be your first best or only option.  Also, there are no 100% results.  Find yourself a doc who specializes in female hair loss and try as many treatments simultaneously as you can since that helps with overall outcomes- the earlier you treat the better the results.

The first step in evaluating hair loss in women, after a detailed history and physical exam, is to rule out any underlying medical causes of hair loss which can be treated. If clinically appropriate, the following disease processes should be considered: anemia, thyroid disease, connective tissue disease, gynecological conditions and emotional stress. Furthermore, over 50% of women going through change of life hormone fluctuations (menopause) experience significant hair loss. It is also important to review the use of medications that may cause hair loss, such as (but not limited to) oral contraceptives, beta-blockers, Vitamin A, thyroid drugs, coumadin, and prednisone. The following laboratory tests have been recommended to rule out the aforementioned medical conditions:
Some common blood tests for female hair loss:
Sex Hormone testsSHBG (Sex Hormone Binding Globulin) used to test status of male hormonesEstradiol is a sex hormoneFSH (Follicle Stimulating Hormone) *not hair follicle but follicle in the ovary*LH (Luteinizing Hormone) is a sex hormoneFree TestosteroneTotal TestosteroneANA (Anti Nuclear Antibody) used to test for Lupus or other autoimmune diseasesTSH (Thyroid Stimulating Hormone) used to test for hyper or hypo-thyroid diseaseTest Iron statusTIBC (Total Iron Binding Capacity)FerritinIron