hello : actually pka of these acidics  unvailable . you can calculate pka from the pH values . 

pKa of  1-Adamantane Carboxylic Acid in BmimNTf2 is 17.0. see: J. Org. Chem. 2013, 78, 12487−12493

Just use a software package to calculate the pKa values. It should give you an idea of the relative strengths of the acids. Pretty sure that Scifinder has one built in.

By first principles and through bond inductive effects, 2,2-dicyclohexylacetic acid and 2-hexyldecanoic acid will have a similar pKa of about 4.8. Presumably 1-Adamantane carboxylic acid would have a higher pKa of ~4.9-5.0

if u have pH of the following acids, u can calculate pKa values of them using Hasselsen Handerbalch equation pH= pKa + log [conjugate base]/[conjugate acid]

You can calculate the pKa values using ChemAxon Package or estimating the value by the following way:

Normaly, the pKa of organic acids in a homologous series of superior members tends to a constant value.

Yes, I agree that ChemAxon could be a suitable package in order to get a guess of pKa values for any compound.

You can calculate it with quantum chemistry software yourself. Here is the detials,

Article Quantum Chemical Calculation of pKas of Environmentally Rele...

I. On the pKa of 2-hexyldecanoic acid (cf. also: decanoic acid; isopalmitic acid; capric acid; isohexadecanoic acid; 14-methylpentadecanoic acid):

a) pKa = 4.9; after: https://en.wikipedia.org/wiki/Decanoic_acid

apud: https://pubchem.ncbi.nlm.nih.gov/compound/2969#section=pKa

apud (pKa = 4.90): Barratt MD; Toxicol In Vitro 10: 85-94 (1996)

b) pKa ≈ 4.9 (predicted); after: https://www.sciencedirect.com/science/article/pii/B9780123821614000042?via%3Dihub

c) Apparent pKa = 6.8 in 'lamellar liquid crystalline phase' (aq. medium); after: Hepatology 4(5) 1984, 77s-79s.

d) pKa (strongest acidic): 4.95 (predicted); after: https://hmdb.ca/metabolites/HMDB0031068

apud: ChemAxon

e) pKa = 4.90±0.40 (predicted); after: https://www.chemicalbook.com/ChemicalProductProperty_EN_cb9144143.htm

f) pKa ≈ 9.0 (fatty acid salts, i.e. soaps, of C16 chain lengths); after:Article Cooperativity among Molecules at Interfaces in Relation to V...

g) pKa = 6.25 (C16 chain lengths fatty acids at membrane/water interface); at:Article Mechanism of Long-Chain Free Fatty Acid Protonation at the M...

II. On the pKa of dicyclohexylacetic acid:

a) pKa = 4.81±0.10 (predicted); after: https://www.chemicalbook.com/ChemicalProductProperty_EN_CB9227778.htm

b) pKa = 4.7 (predicted); after: T.M. Misiti, “Fate and Effect of Naphthenic Acids In Biological Systems”, PhD Thesis, Georgia Inst. of Technol., 2012, p. 206.

c) Gas phase acidity:

Article Acidities of substituted acetic acids

III. On the pKa of 1-adamantanecarboxylic acid (adamantane-3-carboxylic acid):

a) pKa = 4.86±0.20 (predicted); after: https://www.chemicalbook.com/ProductChemicalPropertiesCB3145173_EN.htm

b) pKa ≈ 4.9 (predicted); after: https://www.sciencedirect.com/science/article/pii/B9780123821614000042?via%3Dihub

c) Gas phase acidity:Article Intrinsic acidities of carboxylic acids from gas-phase acid ...

Can. J. Chem., 67(4) 1989, 611-618; https://doi.org/10.1139/v89-092