Recall the condition for Friedel–Crafts reaction

Friedel–Crafts alkylation/acylation proceeds on aromatic rings that are sufficiently reactive toward electrophilic substitution.

Rings do not undergo Friedel–Crafts reactions when:

• they are strongly deactivated by electron-withdrawing groups such as $-NO_2$,
• or the substituent forms a complex with the Lewis acid catalyst (like $AlCl_3$), as in aniline due to the lone pair on $-NH_2$.

Check each compound one by one

(i) Toluene

• Substituent: $-CH_3$
• This is an activating group.
• Hence, undergoes Friedel–Crafts reaction.

(ii) Nitrobenzene

• Substituent: $-NO_2$
• Strongly deactivating group.
• Hence, does not undergo Friedel–Crafts reaction.

(iii) Xylene

• Two methyl groups, both activating.
• Hence, undergoes Friedel–Crafts reaction.

(iv) Cumene

• Isopropyl group is alkyl, hence activating.
• Hence, undergoes Friedel–Crafts reaction.

(v) Aniline

• Substituent: $-NH_2$
• Though $-NH_2$ is activating in ordinary electrophilic substitution, in Friedel–Crafts conditions it forms a salt/complex with $AlCl_3$, making the ring unreactive.
• Hence, does not undergo Friedel–Crafts reaction.

(vi) Chlorobenzene

• Halogens are deactivating, but not so strongly as to completely prevent Friedel–Crafts reaction in the standard JEE classification.
• Chlorobenzene can undergo Friedel–Crafts reaction (though less reactive than benzene).
• Hence, undergoes Friedel–Crafts reaction.

(vii) $m$-Nitroaniline

• Contains both $-NO_2$ and $-NH_2$.
• $-NO_2$ strongly deactivates the ring, and $-NH_2$ also complexes with $AlCl_3$.
• Hence, does not undergo Friedel–Crafts reaction.

(viii) $m$-Dinitrobenzene

• Contains two strongly deactivating $-NO_2$ groups.
• Very strongly deactivated ring.
• Hence, does not undergo Friedel–Crafts reaction.

Count the compounds that cannot undergo Friedel–Crafts reaction

These are:

• Nitrobenzene
• Aniline
• $m$-Nitroaniline
• $m$-Dinitrobenzene

Total number $= 4$

Final answer

$\boxed{4}$