Step 1: Know what conjugate acid means.
A conjugate acid is made by adding one proton ($H^+$) to a given species. So we add one H and raise the charge by one.
Step 2: Look at the given ion.
The species is $H_3P_2O_6^-$. It has a $-1$ charge, so it can grab a proton and act as a base.
Step 3: Add the proton.
\[ H_3P_2O_6^-+H^+\rightarrow H_4P_2O_6 \]
Step 4: Write the new formula.
The conjugate acid is $H_4P_2O_6$, now neutral.
Step 5: Name the acid.
$H_4P_2O_6$ is hypophosphoric acid. It has two phosphorus atoms joined by a P-P bond.
Step 6: State the answer.
\[ \boxed{\text{Hypophosphoric acid}} \]