You can easily find the p value corresponding to a X2 value with our . If you want to find the p value by using a table with critical X2 values, instructions are given below.
Finding $p$ value corresponding to $X^2$ value, using the table with critical $X^2$ values
Assuming a table with a row per degrees of freedom and a column per upper tail probability
$p$ value is the probability of finding the observed $X^2$ value or larger, given that the null hypothesis is true.