Modulo 10 Counter using T flip flops?
You need four T flip flops.
Also, provide clock input to all of them. (synchronous type)
Now,say we  have got 4 outputs say Q1(LSB) ,Q2,Q3 and Q4.

Provide inputs to each flipflop as follows,

T1 =1 ,T2 =Q1 ,T3 =Q2.Q1 and T4 = Q3.Q2.Q1

This will actually work as MOD-16 ( counts 0 TO 15 ) counter.

To make is a MOD-10 counter,

When the output is 1010 (count 10) you need to reset the counters,

SO take outputs Q4 and Q2 connect it to to a NAND gate so that when both are high ,the counters are reset to zero.