Moslem Abarian Please, read some original papers:

Elad, Y., I. Chet, and Y. Henis. "A selective medium for improving quantitative isolation of Trichoderma spp. from soil." Phytoparasitica 9 (1981): 59-67.

Askew, D.J. and Laing, M.D., 1993. An adapted selective medium for the quantitative isolation of Trichoderma species. Plant Pathology, 42(5), pp.686-690.

Isolation of fungi from soil through serial dilution method and from plant through tissue isolation method

You can use the surface sterilisation method with PDA media for growing from the plant.

You can dilute soil and then spread the soil solution in the PDA media.