Thank you so much. It worked 
What I have done is:
class AddnewConvLayer(nn.Module):
    def __init__(self):
        super().__init__()
        self.convolution_layer = nn.Conv2d(32, 3, kernel_size=1)

    def forward(self, x):
        return self.convolution_layer(x)

model.final1 = AddnewConvLayer()
model.final2 = AddnewConvLayer()
model.final3 = AddnewConvLayer()
model.final4 = AddnewConvLayer()