I have 2 SNPs having no association with the disease of interest in our study. I don't know how can I find out which allele is dominant or recessive? There is almost no data about that in previous articles! Is there a database or anything to help me?
Not all variants have either a dominant or a recessive effect. Those terms are just very specific cases of impact on the inheritance of a very limited subgroup of positions. A CFTR F508del mutation is recessive because you only get the disease (cystic fibrosis) if you inherit two deleterious alleles. An APP duplication is dominant because you get the disease (Alzheimer Disease) as soon as you inherit one duplicated allele.
In contrast, most SNPs are just neutral (or have a small effect on the risk of disease) so cannot be classified as either dominant or recessive. Since you write that your SNPs are not associated with the disease then I suspect that your SNPs are in this last category.